Experimental and numerical investigation of flash floods and their interaction with urban settlements

Abstract

Flash floods remain a challenging global problem and due to their dynamic nature combined with their limited spatial and temporal scales. Flash flood modelling is a complex process and numerical simulation of the phenomena requires a deep understanding of the event and complex, three-dimensional modelling if the processes involved are to be replicated to a high level of detail. This thesis explores flash floods and aims to provide further insight into their numerical simulation.

A new dataset for flash floods has been created through a comprehensive set of dam break experiments on ramps of different resistance undertaken in the Department of Mechanical Engineering in University College London (UCL). This dataset illustrates high Froude number flows on slopes and their interaction with buildings and provides further insight into the effect that land use and intensity have on flash flood propagation.

The obtained experimental results were then used to validate a flash flood hydrodynamic model. The numerical investigation was undertaken using the open source software OpenFOAM and its solver interFOAM which showed that the complexity of these events requires different parametrisation for different stages of the process and cannot be described with one set of parameters for the whole progression, thus demonstrating the need for either full 3D simulations or 2D-3D coupled models.

Useful insights regarding the modelling of flash floods were also acquired assessing the Defra and Environment Agency (2010) benchmarking test case for extreme events and comparing the 3D OpenFOAM model’s performance with other industrial software. Finally, through the analysis of applied forces acquired from the experimental and numerical work of flood wave interaction with structures, mitigation strategies were suggested for flood risk in flash flood prone areas.

Date of Award	24 Jun 2020
Original language	English
Awarding Institution	University of Bath
Supervisor	Jun Zang (Supervisor) & Thomas Kjeldsen (Supervisor)